JP6372464B2 - Sheet feeding apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a sheet feeding apparatus that separates and feeds sheet members accommodated in a sheet accommodating portion, and an image forming apparatus including the sheet feeding apparatus.

  A typical image forming apparatus includes a sheet feeding device that feeds a sheet member such as printing paper. The sheet feeding device feeds the uppermost sheet member accommodated in the sheet accommodating portion in the feeding direction by a pickup roller, and feeds the sheet member to the conveyance path by a feeding roller located on the downstream side thereof. In this type of sheet feeding apparatus, there is a case where so-called double feeding occurs in which a plurality of sheet members are picked up and sent out by a pickup roller. 2. Description of the Related Art Conventionally, as a mechanism for preventing double feed, a separation mechanism (see Patent Document 1) using a separation roller that is disposed so as to face a feeding roller is known. In this separation mechanism, the feeding roller is rotated in a state where the separation roller is pressed against the feeding roller with a predetermined urging force.

JP 2009-1113940 A

  However, in the conventional separation mechanism, when the number of times the sheet member is fed increases, the surface of the separation roller is abraded due to contact with the sheet member, the friction coefficient is lowered, and the separation performance may be lowered. If the pressure contact force between the feed roller and the separation roller is increased in anticipation of a decrease in separation performance, the pressure contact force on the thick paper when a thick so-called thick paper is transported to the nip between the feed roller and the separation roller becomes excessive. , There is a risk of poor feeding such as cardboard not being fed.

  The present invention has been made in view of the above circumstances, and its purpose is to reliably prevent double feeding of the sheet member with a simple configuration and to satisfactorily provide the sheet member according to the thickness of the fed sheet member. An object of the present invention is to provide a sheet feeding apparatus that can be separated and an image forming apparatus including the sheet feeding apparatus.

  A sheet feeding apparatus according to one aspect of the present invention includes a sheet storage unit, a feeding roller, a separation roller, a support member, and a first biasing member. The sheet accommodating portion can accommodate a plurality of sheet members. The feeding roller imparts a feeding force in the feeding direction to the sheet member by rotating in contact with the upper surface of the sheet member fed in the predetermined feeding direction from the sheet storage unit. The separation roller is provided below the feeding roller, and is the outermost sheet bundle of a plurality of sheet members fed from the sheet storage portion in a state where a nip portion is formed in contact with the feeding roller. The sheet members other than the upper sheet member can be separated at the nip portion. The support member rotatably supports the separation roller, and the separation roller is configured to be the feeding roller around a swing shaft provided downstream of the rotation shaft of the separation roller in the feeding direction. The separation roller is supported so as to be able to swing between a position where the nip portion can be formed in contact with the sheet and a position where the separation roller is separated from the feeding roller. The first biasing member biases the separation roller in a direction in contact with the feeding roller. The rocking shaft is supported so as to be movable in a separating direction including a tangent line in the nip portion and away from a tangential surface parallel to the rotation shaft.

  An image forming apparatus according to another aspect of the present invention includes the sheet feeding device and an image forming unit that forms an image on a sheet member conveyed by the sheet feeding device.

  According to the present invention, it is possible to reliably prevent double feeding of the sheet member with a simple configuration and to separate the sheet member satisfactorily according to the thickness of the fed sheet member.

FIG. 1 is a diagram showing a configuration of an image forming apparatus according to the first embodiment of the present invention. FIG. 2 is a diagram schematically showing the configuration of the feeding mechanism of the image forming apparatus shown in FIG. FIG. 3 is a diagram illustrating a configuration and an operation state of the feeding mechanism illustrated in FIG. 2. FIG. 4 is a diagram showing a force relationship generated in the feeding mechanism shown in FIG. FIG. 5 is a diagram illustrating a configuration of a feeding mechanism according to the second embodiment of the present invention. FIG. 6 is a diagram illustrating a configuration of a feeding mechanism according to the third embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiment described below is merely an example embodying the present invention, and the embodiment of the present invention can be changed as appropriate without departing from the scope of the present invention.

[First Embodiment]
FIG. 1 is a diagram showing a configuration of an image forming apparatus 10 according to the first embodiment of the present invention. Here, in the following description, the vertical direction 6 is defined with reference to a state in which the image forming apparatus 10 is installed so as to be usable (state in FIG. 1). Further, a front-rear direction 7 is defined with the front side of the image forming apparatus 10 (right side in FIG. 1) as a front, and a left-right direction 8 is defined when the image forming apparatus 10 is viewed from the front side (front side).

[Image forming apparatus 10]
As shown in FIG. 1, the image forming apparatus 10 is a printer that prints an input image on a sheet member using a printing material such as toner. Note that the image forming apparatus 10 is not limited to a printer having only a printing function. For example, the present invention can be applied to a printer, a facsimile machine, a copier, or a multifunction machine having these functions.

  As shown in FIG. 1, the image forming apparatus 10 includes an electrophotographic image forming unit 18, a fixing unit 19, a paper feeding device 15 (an example of a sheet feeding device of the present invention), a conveyance roller 44, and the like. The image forming apparatus 10 includes a control unit 12 that controls the image forming apparatus 10 and a paper discharge unit 21. These are provided on a cover of the outer frame of the image forming apparatus 10 and a housing 14 constituting an inner frame.

  The sheet feeding device 15 is provided at the bottom of the image forming apparatus 10. The sheet feeding device 15 includes a sheet feeding tray 50 (an example of a sheet storage unit of the present invention) and a feeding mechanism 17. The feeding mechanism 17 feeds the sheet member of the paper feed tray 50, and includes a pickup roller 51, a feed roller 52 (an example of the feeding roller of the present invention), and a retard roller 53 (the separation roller of the present invention). For example).

  The sheet feed tray 50 accommodates a sheet member on which an image is formed by the image forming unit 18 and is supported by the housing 14. In the present embodiment, the paper feed tray 50 is supported by the housing 14 so as to be slidable in the front-rear direction 7. As a result, the paper feed tray 50 can move between a position accommodated in the housing 14 and a position drawn forward from the housing 14.

  The paper feed tray 50 is formed in a rectangular box shape having a bottom surface. A plurality of sheet members can be accommodated in the sheet feed tray 50. A lift plate 54 is provided on the bottom surface of the paper feed tray 50, and the lift plate 54 is supported so that the front end portion can be raised from the rear end portion side as a base point. When a driving force is input to the lift plate 54, for example, when the motor is driven and controlled by the control unit 12, the lift plate 54 starts to rise, and the uppermost sheet member in the paper feed tray 50 can be fed. Raised to the feeding position. A sensor (not shown) is provided above the paper feed tray 50, and when the lift plate 54 rises to the feeding position, the control unit 12 receives the output signal of the sensor and stops the lift plate 54 from rising. To do. In addition, when the stacking amount of the sheet members in the sheet feeding tray 50 decreases and the position of the uppermost sheet member decreases, the lift plate 54 is raised again and stopped at the feeding position. By performing such lift control of the lift plate 54, the uppermost sheet member in the paper feed tray 50 is always arranged at the feeding position.

  Specific examples of the sheet member applied to the sheet feeding device 15 include so-called plain paper, so-called thick paper thicker than plain paper, coated paper, postcard, glossy paper, and the like. The sheet feeding device 15 according to the present embodiment is configured so that the sheet member can be reliably separated and fed from the sheet feeding tray 50 without double feeding, regardless of which type of sheet member is accommodated. Has been.

  As shown in FIG. 1, the feeding mechanism 17 is provided above the front portion of the paper feed tray 50. A sheet member is fed from the sheet feeding tray 50 by the feeding mechanism 17.

  The pickup roller 51 is rotatably supported by the roller holder 55. The pickup roller 51 includes a rotation shaft 51 </ b> A extending in the left-right direction 8, and the rotation shaft 51 </ b> A is rotatably supported by the roller holder 55. The pickup roller 51 is supported by the roller holder 55 so as to be positioned above the paper feed tray 50. Specifically, the pickup roller 51 is disposed at a position where the roller surface comes into contact with the uppermost sheet member accommodated in the paper feed tray 50. When a predetermined rotational driving force is input to the rotating shaft 51A and the pickup roller 51 is rotationally driven, the pickup roller 51 feeds the uppermost sheet member of the sheet member pushed up by the lift plate 54 by contact friction. Is granted. Accordingly, the pickup roller 51 sends out the sheet member toward the feed roller 52 on the downstream side in the feeding direction D <b> 1 by the pickup roller 51.

  The feed roller 52 includes a rotation shaft 52A parallel to the rotation shaft 51A of the pickup roller 51. The rotation shaft 51A is rotatably supported by the inner frame of the housing 14. In other words, the feed roller 52 is rotatably supported with the direction orthogonal to the feeding direction by the pickup roller 51 as a rotation axis 52A. In the present embodiment, the roller holder 55 is swingably supported at both ends of the rotation shaft 52A. That is, the rotation shaft 52 </ b> A also serves as the swing shaft of the roller holder 55. The feed roller 52 is disposed downstream of the pickup roller 51 in the feeding direction D1. For this reason, the roller holder 55 is swingable about the rotation shaft 52A by being supported by the rotation shaft 52A. As a result, the roller holder 55 can swing in a direction in which the roller surface of the pickup roller 51 is in contact with or separated from the uppermost sheet member.

  The feed roller 52 is disposed at a position where the roller surface comes into contact with the sheet member sent out by the pickup roller 51. When the rotational driving force from the motor is input to the rotating shaft 52A and the feed roller 52 is rotationally driven, the feed roller 52 gives the sheet member fed by the pickup roller 51 a feeding force by contact friction, The sheet member is fed to the first conveyance path 26 on the downstream side in the feeding direction D1. A transmission mechanism such as a gear or a belt is interposed between the rotation shaft 52A of the feed roller 52 and the rotation shaft 51A of the pickup roller 51, and the rotational driving force input from the motor to the rotation shaft 52A is It is transmitted to the rotating shaft 51A via the transmission mechanism.

  FIG. 2 is a schematic diagram of the feeding mechanism 17. In FIG. 2, the pickup roller 51 and the roller holder 55 are not shown. As shown in FIG. 2, the retard roller 53 is provided below the feed roller 52. The retard roller 53 is supported by a retard holder 60 described later. By being supported by the retard holder 60, the retard roller 53 comes into contact with the roller surface of the feed roller 52 and forms a nip portion 79 with the feed roller 52. The retard roller 53 is used as an application for separating the other sheet member from the uppermost sheet member among the plurality of sheet members when a plurality of sheet members are sent out at once by the pickup roller 51. The retard roller 53 and its support mechanism will be described later.

  An elastic member 58 having a predetermined hardness is provided on the outer periphery of the retard roller 53. The elastic member 58 is smaller than the hardness of the surface of the feed roller 52, and, for example, urethane rubber having an elastic force measured by a durometer type A type rubber hardness tester defined in JIS standards within a range of 25 to 50 degrees. It consists of That is, the outer peripheral surface of the retard roller 53 is formed of a material that is softer and more elastic than the surface of the feed roller 52. Note that materials other than urethane rubber, such as nitrile rubber, chloroprene rubber, and silicon sponge, may be applied as long as the hardness falls within the range of 25 degrees to 50 degrees.

  The retard roller 53 is provided with a torque limiter 74. The torque limiter 74 is attached to the rotation shaft 53 </ b> A of the retard roller 53. The torque limiter 74 is connected to the retard roller 53 and applies a static torque when the rotating shaft 53A of the retard roller 53 receives torque less than a predetermined set value. On the other hand, when the rotating shaft 53A receives a torque greater than the set value, the connection with the retard roller 53 is disconnected to interrupt the transmission of the stationary torque so that the retard roller 53 can rotate with respect to the rotating shaft 53A. To do.

  When an instruction to start the sheet member feeding operation is input to the image forming apparatus 10, the feed roller 52 and the pickup roller 51 are driven to rotate, and the sheet member is fed from the sheet feeding tray 50. When the sheet member fed from the paper feed tray 50 by the pickup roller 51 in the feeding direction D1 reaches a position where the sheet can be fed by the feed roller 52, the sheet member is further fed downstream by the feed roller 52 in the feeding direction D1. Sent. When the sheet member reaches the conveying roller 44 disposed on the downstream side of the feed roller 52, the rotation of the pickup roller 51 and the feed roller 52 is stopped at that timing. Thereafter, the sheet member is conveyed along the first conveyance path 26 (see FIG. 1) only by the conveyance roller 44. Note that when the sheet member is conveyed only by the conveying roller 44, the pickup roller 51 has a built-in one-way clutch, and therefore its rotation is stopped. Further, when the sheet member is not double-fed at the time of feeding by the pickup roller 51, the feed roller 52 and the retard roller 53 are driven to rotate by the conveyance of the sheet member. The retard roller 53 is provided with a torque limiter 74, and is pressed against the feed roller 52 by a coil spring 71 (see FIG. 3) described later. For this reason, a sufficient frictional force is generated between the retard roller 53 and the sheet member, and the driven roller rotates against the static torque of the torque limiter 74. On the other hand, when the sheet member is double-fed at the time of feeding by the pickup roller 51, the feed roller 52 is driven and rotated by the conveyance of the sheet member. However, the retard roller 53 is stopped by the stationary torque of the torque limiter 74 together with the other sheet members excluding the uppermost sheet member among the plurality of sheet members (corresponding to the sheet bundle) that are double-fed. Thereby, the retard roller 53 prevents the other sheet member from being carried along the uppermost sheet member. The uppermost sheet member is conveyed while sliding while in contact with the stopped lower sheet member.

  As shown in FIG. 1, the image forming unit 18 is provided near the end of the first conveyance path 26. The image forming unit 18 forms a toner image on the sheet member based on image data input from the outside. Specifically, the image forming unit 18 transfers the toner image to the sheet member using toner. The image forming unit 18 includes a photosensitive drum 31, a charging unit 32, a developing unit 33, a transfer unit 35, a cleaning unit 36, and an LSU (Laser Scanning Unit) 34 as an exposure unit. When the image forming operation is started, the charging unit 32 charges the surface of the photosensitive drum 31 to a uniform potential. Further, laser light is scanned on the photosensitive drum 31 charged from the LSU 34 according to the image data. Thereby, an electrostatic latent image is formed on the photosensitive drum 31. Thereafter, toner is attached to the electrostatic latent image by the developing unit 33, and the toner image is developed on the photosensitive drum 31. Then, the toner image is transferred by the transfer unit 35 to the sheet member conveyed by the conveyance roller 44 through the first conveyance path 26. The sheet member on which the toner image is formed is conveyed to the second conveyance path 27 formed on the downstream side of the image forming unit 18 in the conveyance direction of the sheet member.

  The second conveyance path 27 extends to the rear of the image forming apparatus 10, and the fixing unit 19 is provided at the end thereof. The sheet member sent from the image forming unit 18 to the second conveyance path 27 is conveyed to the fixing unit 19 through the second conveyance path 27. The fixing unit 19 fixes the toner image transferred to the sheet member to the sheet member by heat and pressure, and includes a heating roller 41 and a pressure roller 42. When the sheet member passes through the fixing unit 19, the fixing unit 19 fixes the toner image to the sheet member and forms an image on the sheet member. Thereafter, the sheet member is conveyed to a third conveyance path 28 formed downstream of the fixing unit 19 in the conveyance direction of the sheet member.

  The third conveyance path 28 is curved upward from the fixing unit 19 and then extends straight upward, and is further curved forward to reach the paper discharge port 22. That is, the third transport path 28 is formed between the fixing unit 19 and the paper discharge port 22. The third transport path 28 is provided with a plurality of paper discharge roller pairs 23 that are rotationally driven. The sheet member conveyed to the third conveyance path 28 is conveyed upward through the third conveyance path 28 by a pair of rotationally driven paper discharge rollers 23 and is provided on the upper surface of the image forming apparatus 10 from the paper discharge port 22. The paper is discharged to the discharged paper discharge unit 21.

  Hereinafter, with reference to FIG.2 and FIG.3, the detail of the retard roller 53 and its support mechanism is demonstrated.

  As shown in FIG. 2, the feeding mechanism 17 includes a retard holder 60 that supports the retard roller 53 (an example of a support member of the present invention), and a coil spring 71 that applies an urging force to the retard holder 60 (first of the present invention). An example of one urging member).

  The retard holder 60 rotatably supports the retard roller 53. Specifically, the retard holder 60 includes a retard roller 53 and a housing portion 61 that rotatably supports the retard roller 53. The accommodating portion 61 is partitioned by a pair of side walls 63 that are separated in the left-right direction 8 and a bottom plate 64 that connects the lower ends of the side walls 63.

  The retard roller 53 has a rotation shaft 53 </ b> A that extends in the same direction as the axial direction of the pickup roller 51 and the feed roller 52. A shaft hole (not shown) is formed on the rear side of the side wall 63, and the rotation shaft 53A is fixed to the shaft hole. The retard roller 53 is rotatably supported on the rotation shaft 53A.

  The retard holder 60 has a swing shaft 65. The swing shaft 65 is provided on the downstream side (front side in FIG. 2) in the feeding direction D1 with respect to the rotation shaft 53A of the retard roller 53. The swing shaft 65 passes through a through hole formed on the front side of the side wall 63, and both ends thereof are supported by a support plate 80 described later. The swing shaft 65 is fixed to the side wall 63 by the through hole. Specifically, a fixed bush 67 is provided in the through hole, and the swing shaft 65 is fixed to the side wall 63 by the fixed bush 67. Thereby, the retard holder 60 is supported so as to be swingable about the swing shaft 65. In the present embodiment, the retard holder 60 includes a contact position (position shown in FIG. 2) where the retard roller 53 can contact the peripheral surface of the feed roller 52 to form the nip portion 79, and the retard roller 53 is the feed roller 52. It is supported so as to be able to swing between the separated position and the separated position.

  The sheet feeding device 15 includes a pair of support plates 80 that support the swing shaft 65. The support plate 80 is provided outside the side walls 63 of the retard holder 60. The support plate 80 constitutes a part of the internal frame of the housing 14 (see FIG. 1), for example. The support plate 80 has a long hole 84 that is long in the vertical direction 6. Both ends of the swing shaft 65 are inserted into the long hole 84. Thus, the swing shaft 65 is supported so as to be movable in the vertical direction 6. Specifically, as shown in FIG. 3A, the support plate 80 supports the swing shaft 65 so as to be movable in a separating direction away from the contact surface S1. Here, the contact surface S1 is a contact surface that includes a tangent line in the nip portion 79 and is parallel to the rotation shaft 53A in a non-feed state in which the sheet member is not fed by the feed roller 52.

  As shown in FIG. 3, the support plate 80 is provided with a coil spring 82 (an example of a second urging member of the present invention) that urges the swing shaft 65 in the proximity direction approaching the contact surface S <b> 1. The coil spring 82 is provided inside the long hole 84. Specifically, the coil spring 82 is provided between the lower end 84 </ b> A of the long hole 84 and the swing shaft 65. The coil spring 82 is a so-called compression spring, and applies a biasing force that biases the swing shaft 65 upward, that is, a biasing force that biases the swing shaft 65 in the proximity direction. Thereby, the swinging shaft 65 receives the biasing force and maintains a state of contacting the upper end 84 </ b> B of the long hole 84 when no external force is applied.

  As shown in FIG. 3A, in a state where the retard holder 60 is in the contact position, the swing shaft 65 is formed by an angle α formed by a straight line connecting the rotation shaft 53A and the swing shaft 65 and the contact surface S1. Is within a range of 5 to 15 degrees. For this reason, the retard roller 53 that rotates following contact with the feed roller 52 generates a biting force F <b> 10 whose peripheral surface tries to bite into the feed roller 52. The biting force F10 is a force generated when the feed roller 52 is rotationally driven in a configuration in which the retard roller 53 is swingably held by the swing shaft 65 at a position different from the rotation shaft 53A. . Specifically, when the feed roller 52 is rotationally driven in the counterclockwise direction in FIG. 3, the frictional force caused by contact with the retard roller 53 on which a static torque is applied by the torque limiter 74 (see FIG. 2). F11 (see FIG. 3A) occurs. The friction force F11 is not only the friction force when the feed roller 52 and the retard roller 53 are in direct contact, but also the sheet member in a state where the sheet member is interposed between the feed roller 52 and the retard roller 53. Including frictional force. And the component force of the rotation direction of the retard holder 60 in the friction force F11 acts so as to press the retard roller 53 against the feed roller 52 side. This pressing force is applied between the feed roller 52 and the retard roller 53 as the biting force F10 together with a biasing force F20 of the coil spring 71 described later.

  Here, the biting force F10 is F12 (see FIG. 4), which is a force generated in the tangential direction D11 from the nip portion 79 toward the swing shaft 65 along the contact surface S1 when the feed roller 52 is driven to rotate. When the angle β formed by S1 and the straight line L1 is θ, it can be expressed by the following equation (1).

  F10 = F12 * tan θ (1)

  Here, as shown in FIG. 4, the force F <b> 12 is a force generated in the nip portion 79 as a force in the tangential direction D <b> 11 with respect to the upper surface of the sheet member when the sheet member exists in the nip portion 79. It is. This force F12 acts on the retard holder 60 via the nip 79 and the retard roller 53 and the rotation shaft 53A (see the dotted arrow in FIG. 4).

  The magnitude of the force F12 is equal to the force obtained by adding the static torque received from the torque limiter 74 to the frictional force F11 generated in the sheet member at the nip portion 79. This force F12 acts on the sheet member as a force for conveying the sheet member in the tangential direction D11. When the set value of the torque limiter 74 is M and the radius of the retard roller 106 is r, the rotational torque F12 * r when the retard roller 106 is driven to rotate is equal to the set value M (F12 * r = M). On the other hand, in the nip portion 79, the downward vertical drag that the retard roller 53 receives from the feed roller 52 is N, the distance between the rotation shaft 53A and the swing shaft 65 is X, and the contact surface S1 to the swing shaft 65 If the distance of Y is Y, the following equation (2) indicating the balance of forces around the fulcrum of the swing shaft 65 is established.

  (F20−N) * X + M−F12 (r−Y) = 0 (2)

  Substituting F * r = M into the equation (2) and arranging the vertical drag N results in the following equation (3).

N = F12 (Y / X) + F20
= F12 * tan θ + F20 = F10 + F20 (3)

  That is, as shown in the equation (3), it can be understood that the vertical drag N includes the biting force F10 (= F12 * tan θ) in addition to the urging force F20 of the coil spring 71.

  The coil spring 71 biases the retard roller 53 in a direction in contact with the peripheral surface of the feed roller 52 by applying a biasing force to the retard holder 60. Specifically, the coil spring 71 is provided between the bottom plate 64 of the retard holder 60 and the spring receiver 75. The spring receiver 85 constitutes a part of the inner frame of the housing 14 (see FIG. 1), and is provided below the bottom plate 64. In the present embodiment, the upper end of the coil spring 71 is connected to the upstream side (the rear side in FIG. 3) in the feeding direction D1 with respect to the swing shaft 65 in the bottom plate 64. The coil spring 71 is a so-called compression spring and urges the rear side of the retard holder 60 upward. As described above, the retard roller 53 is provided on the rear side of the retard holder 60. Therefore, when the coil spring 71 urges the retard holder 60 upward, the retard holder 60 receives the urging force and maintains the contact position when no external force is applied. The coil spring 71 only needs to apply a biasing force that brings the retard roller 53 into contact with the peripheral surface of the feed roller 52 to the retard holder 60. For example, the coil spring 71 is provided between the support plate 80 and the retard holder 60. A coil spring or a torsion coil spring may be used.

  Since the feeding mechanism 17 is configured in this way, as shown in FIG. 3A, when the sheet member does not enter the nip portion 79, the upward biasing force F20 by the coil spring 71 is received. Thus, the retard holder 60 is maintained at the contact position where the retard roller 53 contacts the peripheral surface of the feed roller 52. The angle β formed by the contact surface S1 and the straight line L1 at this time is defined as an angle θ1. Here, the angle θ1 is an angle within a range larger than 0 ° and smaller than 90 ° (0 ° <θ1 <90 °). The straight line L <b> 1 passes through a contact point (contact point between the retard roller 53 and the feed roller 52) in the nip portion 79 and the center of the swing shaft 65.

  In the conventional separation mechanism, when the number of fed sheet members increases, the surface of the retard roller 53 wears, the friction coefficient decreases, and the separation performance deteriorates. When conveyed to the part 79, there is a case where sufficient frictional force is not generated between the retard roller 53 and the lower sheet member, and the sheet member cannot be separated. On the other hand, when the pressure contact force between the feed roller 52 and the retard roller 53 is increased in anticipation of a decrease in separation performance due to abrasion, when a so-called thick paper having a relatively large thickness is conveyed to the nip portion 79, The press contact force becomes excessive, and there is a risk of causing a feeding failure such as the cardboard not being fed.

  In this embodiment, when the sheet member is fed by the pickup roller 51 and enters the nip portion 79, the sheet member presses the retard roller 53 downward against the biasing force of the coil spring 71. At this time, a downward pressing force also acts on the retard holder 60 via the rotating shaft 53A of the retard roller 53. This downward pressing force pushes down the swing shaft 65 in the direction (downward) away from the contact surface S1 against the urging force of the coil spring 82. The urging forces of the coil spring 71 and the coil spring 82, the position of the rotating shaft 53A with respect to the swing shaft 65, the weight of the retard holder 60, and the like are determined so that the retard holder 60 is pushed downward by the pressing force. . When the swing shaft 65 is pushed down in the long hole 84, the angle β formed by the contact surface S1 and the straight line L1 becomes an angle θ2 larger than the angle θ1. Here, the angle θ2 is an angle within a range larger than 0 ° and smaller than 90 °. The straight line L <b> 1 passes through the contact point (contact point between the sheet member and the feed roller 52) in the nip portion 79 and the center of the swing shaft 65. That is, when the sheet member enters the nip portion 79, the swing shaft 65 moves so that the angle β becomes the angle θ2 larger than the angle θ1. As described above, when the sheet member enters the nip portion 79, the angle β is increased, so that the biting force F10 is increased. Note that the biasing force F20 of the coil spring 71 is increased by the downward movement of the retard holder 60, which is too small compared to the increase of the biting force F10.

  For this reason, even when the sheet member is double-fed, the biting force F <b> 10 increases due to the sheet member entering the nip portion 79. Therefore, even if the surface of the retard roller 53 is worn and the friction coefficient is lowered, a sufficient frictional force is generated between the sheet member and the retard roller 53, so that the separation performance is not lowered, and multiple feeding is performed. It can prevent suitably. Further, when a relatively thick sheet member (so-called thick paper) is double-fed, the greater the thickness of the sheet member, the larger the angle β, so the biting force F10 increases. For this reason, even when thick paper is double-fed, the separation performance does not deteriorate and double-fed can be prevented. That is, in the sheet feeding device 15 of the present embodiment, the sheet member can be favorably separated according to the thickness of the fed sheet member.

  In the above-described embodiment, the long hole 84 has a shape that is long in the vertical direction, but the long hole 84 may have a shape that is long in a direction perpendicular to the straight line L1. In this case, the degree of enlargement of each β with respect to the amount of movement that moves in the long hole 84 of the swing shaft 65 is greater than in the case of a shape that is long vertically. Further, the long hole 84 may have a long arc shape along a virtual circular arc passing through the center of the swing shaft 65 with the nip portion 79 as a center point.

[Second Embodiment]
Hereinafter, a feeding mechanism 17A according to a second embodiment of the present invention will be described with reference to FIG. The feeding mechanism 17A according to the second embodiment of the present invention differs from the first embodiment described above in that a solenoid 90 (an example of the drive unit of the present invention) is provided and no coil spring 82 is provided. Is a point.

  As shown in FIG. 5, the solenoid 90 has a plunger 91. The solenoid 90 has a distal end of a plunger 91 connected to the swing shaft 65 via a link member 92 in order to apply a driving force to the retard holder 60. The solenoid 90 protrudes when the drive signal is input, and when the drive signal is interrupted, the solenoid 90 pulls the plunger 91 back to the original position by a built-in tension spring. The drive of the solenoid 90 is controlled by the control unit 12 (see FIG. 1).

  The link member 92 is connected to the swing shaft 65 so that the plunger 91 can press the swing shaft 65 in the separating direction. Specifically, in a state where the solenoid 90 is not driven, one end of the link member 92 is connected to the swing shaft 65, and the other end is planned at a position higher than the height position of the swing shaft 65. It is connected to the tip of the jar 91.

  In the present embodiment, the control unit 12 controls the solenoid 90 to move the swing shaft 65 in the separation direction when a sheet member (so-called thick paper) having a predetermined thickness or more is accommodated in the paper feed tray 50. A driving force for moving to the rocking shaft 65 is applied via the link member 92. Whether or not a sheet member having a predetermined thickness is stored in the sheet feeding tray 50 is determined based on, for example, sheet type information registered in advance in the image forming apparatus 10 by the user. The sheet type information is information including the thickness of the sheet member accommodated in the paper feed tray 50 and is stored in a storage unit included in the control unit 12. Further, when the print job information input to the image forming apparatus 10 includes the thickness information of the sheet member, the determination can be made based on the print job information.

  FIG. 5A shows a state where the solenoid 90 is not driven, and FIG. 5B shows a state where the solenoid 90 is driven. As shown in FIG. 5A, the retard holder 60 maintains the contact position when the solenoid 90 is not driven. In this state, when the control unit 12 outputs a drive signal to the solenoid 90, the plunger 91 of the solenoid 90 protrudes and the link member 92 operates the swing shaft 65. Specifically, the swing shaft 65 moves in the separating direction by the protrusion of the plunger 91. As a result, the retard holder 60 swings in the clockwise direction in FIG. In addition, since the retard roller 53 is biased upward by the biasing force of the coil spring 71, the retard roller 53 maintains a state in contact with the feed roller 52. At this time, as shown in FIG. 5B, the angle β is expanded to an angle θ2 larger than the angle θ1, so that the biting force F10 increases.

  Thus, since the feeding mechanism 17A is configured, even if the frictional force of the retard roller 53 with respect to the sheet member is reduced and the biting force F10 before increasing cannot separate the thick paper, Only when feeding, the rocking shaft 65 of the retard holder 60 moves in the separating direction and the biting force F10 increases. For this reason, even when thick paper is fed in a multiple manner, it is possible to reliably separate the thick paper without being affected by the reduction in frictional force of the retard roller 53.

  In the above-described embodiment, the solenoid 90 is illustrated as an example of the drive unit, but a drive unit such as a motor may be applied instead of the solenoid 90.

[Third Embodiment]
Hereinafter, a feeding mechanism 17B according to a third embodiment of the present invention will be described with reference to FIG. The feeding mechanism 17B of the third embodiment of the present invention is different from the second embodiment described above in that a rotary encoder 95 for detecting whether or not the retard roller 53 rotates on the rotating shaft 53A of the retard roller 53 (this book) An example of the rotation detection sensor of the invention is provided.

  The rotary encoder 95 outputs a detection signal corresponding to the rotational speed of the retard roller 53 to the control unit 12. The control unit 12 determines whether the retard roller 53 is rotating or stopped based on the detection signal. Moreover, the control part 12 determines the rotation speed, when the retard roller 53 is rotating.

  For example, when the friction force with respect to the sheet member of the retard roller 53 is sufficient, when one sheet member enters the nip portion 79, the retard roller 53 rotates at the same rotational speed (rotational speed) as the feed roller 52. To do. On the other hand, when the frictional force is sufficient, the retard roller 53 stops when the sheet member is conveyed to the nip portion 79 in a state where the sheet member is double fed. In this case, it is considered that the sheet member is correctly separated. On the other hand, when the friction force with respect to the sheet member of the retard roller 53 is insufficient, specifically, when the friction force with respect to the sheet member of the retard roller 53 is smaller than the friction force between the sheet members, the sheet member is double-fed. Even if the sheet member is conveyed to the nip portion 79, the sheet member in contact with the retard roller 53 slips, so that the sheet member does not stop and is conveyed while the sheet member is double fed. Further, in this case, the retard roller 53 becomes unstable in rotation due to slippage or the like generated between the sheet member, and as a result, rotates at a speed slower than the rotation speed of the feed roller 52. In this case, the controller 12 can determine that the rotational speed of the retard roller 53 is slower than the rotational speed of the feed roller 52 based on the detection signal from the rotary encoder 95 when the feed roller 52 is rotationally driven. . At this time, the control unit 12 drives the solenoid 90 to move the swing shaft 65 in the separation direction.

  Thus, since the feeding mechanism 17B is configured, the angle β is expanded to an angle θ2 larger than the angle θ1 when the swing shaft 65 is moved in the separation direction by the control unit 12. The biting force F10 increases. As a result, even when the frictional force of the retard roller 53 with respect to the sheet member decreases due to wear or the like and the separation performance decreases, the biting force F10 increases, so that the sheet member can be reliably prevented from being double fed.

10: image forming device 12: control unit 15: paper feeding device 17A, 17B: feeding mechanism 18: image forming unit 19: fixing unit 44: transport roller 50: paper feed tray 51: pickup roller 52: feed roller 53: retard Roller 58: Elastic member 60: Retard holder 74: Torque limiter 79: Nip part 90: Solenoid

Claims (5)

A sheet accommodating portion capable of accommodating a plurality of sheet members;
A feeding roller that applies a feeding force in the feeding direction to the sheet member by rotating in contact with the upper surface of the sheet member fed in a predetermined feeding direction from the sheet storage unit;
The uppermost sheet member among a plurality of sheet members which are provided below the feeding roller and are fed from the sheet storage unit in a state where a nip portion is formed in contact with the feeding roller. A separation roller capable of separating the sheet member other than at the nip portion;
The separation roller is rotatably supported, and the separation roller is in contact with the feeding roller around a swing shaft provided on the downstream side in the feeding direction with respect to the rotation shaft of the separation roller. A support member supported so as to be swingable between a position where a nip portion can be formed and a position where the separation roller is separated from the feeding roller;
A first urging member that urges the separation roller in a direction in contact with the feeding roller;
The swing shaft is supported so as to be movable in a separating direction including a tangent line in the nip portion at the time of non-feeding and away from a contact surface parallel to the rotation shaft,
A second urging member for urging the swing shaft in a proximity direction approaching the contact surface;
Each of the first urging member and the second urging member is moved so as to move the swing shaft downward when the sheet member having a predetermined thickness or more is fed to the sheet accommodating portion. A sheet feeding device in which an urging force is set. A sheet accommodating portion capable of accommodating a plurality of sheet members;
A feeding roller that applies a feeding force in the feeding direction to the sheet member by rotating in contact with the upper surface of the sheet member fed in a predetermined feeding direction from the sheet storage unit;
The uppermost sheet member among a plurality of sheet members which are provided below the feeding roller and are fed from the sheet storage unit in a state where a nip portion is formed in contact with the feeding roller. A separation roller capable of separating the sheet member other than at the nip portion;
The separation roller is rotatably supported, and the separation roller is in contact with the feeding roller around a swing shaft provided on the downstream side in the feeding direction with respect to the rotation shaft of the separation roller. A support member supported so as to be swingable between a position where a nip portion can be formed and a position where the separation roller is separated from the feeding roller;
A first urging member that urges the separation roller in a direction in contact with the feeding roller;
The swing shaft is supported so as to be movable in a separating direction including a tangent line in the nip portion at the time of non-feeding and away from a contact surface parallel to the rotation shaft,
A drive unit for transmitting a drive force for moving the swing shaft in the vertical direction;
A control unit that applies a driving force to control the driving unit to move the swing shaft in the separation direction when the sheet member having a thickness greater than or equal to a predetermined thickness is fed to the sheet storage unit; further comprising Cie over preparative feeding device.   The sheet feeding device according to claim 2, wherein the drive unit is a solenoid having a plunger, and the plunger is coupled to the swing shaft so as to be able to press the swing shaft in the separation direction. A rotation detection sensor is provided on the rotation shaft of the separation roller;
The control unit controls the drive unit when the rotation detection sensor detects that the rotation speed of the rotation shaft is less than the rotation number of the feeding roller during rotation driving of the feeding roller. The sheet feeding apparatus according to claim 2, wherein a driving force for moving the swing shaft in the separation direction is applied. A sheet feeding device according to any one of claims 1 to 4,
An image forming apparatus comprising: an image forming unit that forms an image on the sheet member conveyed by the sheet feeding device.

Images